The subject matter of this invention is a device for moving gas, especially related to the suction extraction of gas for gas atmospheres in systems that produce coatings on substrates.
Substrates are frequently coated with thin layers of one element or with compounds with the PECVD process (plasma enhanced chemical vapour deposition) or with the PVD process (physical vapour deposition) in the solar and semiconductor industries. Sputtering, thermal vaporization, laser and ion-beam vaporization, plasma coatings and other processes known from the prior art are used here. These processes are frequently carried out in continuous-operation systems that have processing chambers designed in the form of vacuum chambers; the substrates to be coated are moved through them in a continuous or discontinuous (step-by-step) fashion and coated in the process.
The coating or other working materials are frequently in a gaseous form. Portions that are not deposited on the substrate can therefore spread out in the treatment chamber in an uncontrolled fashion. It is therefore desirable to suction off these gases in a controlled manner without interference with the coating or processing actions caused by flow profiles.
Several layers of different materials are frequently applied to a substrate in direct succession. It is advantageous in cases of that type when there is no requirement for complex inward and outward transfers in different treatment chambers, but instead when the successive coatings can be performed in one and the same treatment chamber. It can be problematic here when the various coating materials are not compatible with one another and, for instance, react with one another in an undesirable way or when components of a coating material act as an impurity in the layer of a different material.
A series of technical approaches exist to solve this problem. In addition to small intermediate lock chambers and movable boundaries, the procedure of preventing the overflow of gaseous materials from one chamber area to another has especially prevailed. The gas flow is suctioned up for this, preferably at the boundaries of the treatment areas, and a separation of areas is achieved in that way.
WO2007/059749 describes a system with small intermediate lock chambers that the substrates are moved through via the transport system and that have flaps that alternatively cover the inlet or outlet opening of the intermediate lock chambers. Suctioning takes place in the lock-chamber area to remove the gas residues that are also transported.
DD214865A1 describes how separation is achieved between two coating areas in which work is one with plasmatrons; a first area has a highly reactive working gas, and the second area has a working gas with little reactivity; separation is achieved by increasing the pressure of the gas with little reactivity. Furthermore, suctioning is provided between the two areas. This prevents the highly reactive gas from penetrating into the second area.
A coating system for glass substrates is disclosed in DE4303462A1 in which the glass substrates are coated from above in a horizontal position in a continuous process. The coating areas are also separated here by providing suction units between them. In the solution that is described, suction takes place downwards from the bottom of the substrates and, in other embodiments, there is simultaneously suction between the coating areas, lateral to the targets from which the coating material is removed. On top of that, intermediate walls are used together with the other construction elements of the coating chamber that form a tube-like hollow area that has a rectangular cross-section. This hollow area has a slot acting as a gas inlet that is turned towards the side on which the target is located. The hollow area is evacuated via a vacuum pump at its ends on the side wall of the coating chamber.
The two devices according to DD214865A1 and DE4303462A1 have the common feature that gas is suctioned out of the coating chambers without consideration being given to the flow conditions that arise. It can therefore be expected that a gas flow that is very much stronger will arise in the proximity of the pump opening than at some distance to it. Since the pumps are typically in the side wall of the treatment chamber or are arranged over or under the substrate, a more even gas flow over the entire substrate that avoids influencing the coating process a bit cannot be expected.
DE102010028734A1 envisages the realization of gas separation between two coating areas by providing suction through an opening directly above the substrate surface that is flanked by metal sheets aligned in parallel with the substrate surface and intended to create flow resistance. Since the pressure loss is much greater around these flow-resistance sheets than the pressure loss behind them, the inventors think that they have achieved an evening out of the flow profile over the entire length of the suction device. The length of the suction device is to be viewed as perpendicular to the transport direction of the substrates and parallel to their surface. The suctioning is done via vacuum pumps that are arranged above the substrates.
DE 10 2008 026 001 B4 claims a method for creating a process atmosphere in continuous coating systems. In particular, it is envisaged that at least two coating areas will exist in the coating system that can have different gas atmospheres. The gas atmospheres are separated by providing a gas-supply unit and a gas-extraction system in every coating area. Furthermore, there is a description that the gas-extraction system is to be “created in the form of a gas channel (16) that extends over the substrate width, crosswise to the direction of transport (3) of the substrate (1) and that has at least one opening (20) so that the gas flow (22) is distributed between the substrate (1) and the gas channel (16) and over the width of the substrate”. It is envisaged that a gas channel for gas supply will be located on the side of the coating source and that a gas channel for gas extraction will be located on the other side.
The customary arrangement of vacuum pumps directly above the substrates in the prior art prevents a structure that provides for several treatment areas on top of one another. Moreover, the suction extraction causes, because of the gap between the substrate and the flow guide plates, a strongly inhomogeneous flow that can lead to an uneven coating of the substrate surface. Especially in the case of plasma processes, for instance plasma etchings or a PECVD process, decomposition products or gas particles generated in the plasma sometimes have the characteristic of being able to also trigger reactions with the substrate surfaces in remote areas outside of the defined processing area. That can lead to disadvantageous changes to the surface characteristics, for instance changes to the homogeneity or to the passivation quality or optical properties etc.